After the terror event happened on Sep. 11, 2001 in the US, all countries are all attaching much more importance to the examination of the luggage of passengers than ever before.
Nowadays, there are two types of article detection apparatus used in railway stations and airports, one type being a DR (digital radiographic) detection apparatus, and the other being a CT (computer tomography) detection apparatus.
As we all know, the DR detection apparatus can obtain a two-dimensional projection image of the article to be examined, therefore, it can examine the articles at very high speed and can easily detect a dangerous metal article. However, since the two-dimensional projection image of the article contains relatively less information than a three-dimensional projection image of the article, the DR detection apparatus can not accurately judge whether there contains an explosive in an article of luggage.
Compared with the DR detection apparatus, the CT detection apparatus can rebuild a three-dimensional projection image of the article based on the projection data by using the CT rebuild arithmetic, therefore, the CT detection apparatus can accurately judge whether there contains the explosive in the luggage. However, the examination speed of the CT detection apparatus is very slow and can not satisfy the need of quickly detecting the luggage.
In order to accurately examine the luggage at high speed, a detection device having a DR apparatus and a CT apparatus recently was proposed. The detection device firstly performs prejudgment on the detected article at a relatively high speed by using the DR apparatus. If the result of the prejudgment indicates there may be a suspicious region where a dangerous article may be hidden in the luggage, then the CT apparatus performs re-judgment on the suspicious region so as to accurately and finally determine whether a dangerous article is hidden in the region. However, since the detection accuracy of the DR apparatus is very poor, the DR apparatus still misses some real dangerous articles or mistakes a safe article as a dangerous during the prejudgment.